The invention relates generally to a mechanical screw press apparatus of the type for continuous operation to process and extrude polymeric materials for forming a pellet-like product which can thereafter be further processed, such as by baling or the like, into a further product, such as sheet, strip, or the like. The invention more specifically relates to a new and novel screw press cage assembly which may be located upstream of the extruder portion of the press which, in effect, provides a fluid discharge or vent section for dewatering and otherwise moving moisture from the polymeric process material.
Heretofore, various apparatus generally characterized as mechanical screw press devices have been provided for the removal of moisture, vapors, etc. from polymeric materials, and for the subsequent production of porous pellets or similar products from the processed polymeric material. Such devices have generally included a screw press having a screw press cage to which the polymeric material is advanced wherein the material is compressed and moved through the cage and then extruded through an extruder portion of the press to produce a product essentially free of moisture, vapors, etc., which is suitable for baling or for further processing into ultimate product form.
A typical prior art apparatus of this type for removing moisture are illustrated in U.S. Pat. Nos. 3,225,453; 3,382,538; 3,518,936; 3,574,891 and 3,672,641.
In such apparatus and/or process methods, a substantial amount of liquid, such as retained water, resides in the polymeric material at it discharges from the press.
In the past, it has been recognized that if a considerable amount of liquid, such as retained water, is retained in the polymeric material as it is delivered from the press, there results a relatively active discharge of liquid from the polymeric material. This occurrence results, as believed, from the pressure differential as the polymeric material is extruded from the press which, in turn, produced relatively small particles ("fines") formed from the polymeric material within the press. As will be seen, these "fines" act not only to contaminate, such as by clogging or the like, components of the press including the screw press cage assembly but also may contaminate the ultimate product to be produced for subsequent baling or the like. Accordingly, there exists a need for a screw cage assembly which can be quickly and easily cleaned and/or repaired in the event that some of the fluid apertures (vents) become blocked and/or clogged so as to minimize the amount of down-time of the press while these components are being cleaned, repaired, or replaced.
In the past, in such mechanical screw press apparatus difficulties have been encountered in respect to installation and/or removal of various components of the cage assemblies for purposes of cleaning, i.e. removal of the "fines," and for purposes of repair and/or replacement. For example, in prior apparatus it has been the requirement to disassemble the entire cage assembly, such as by unbolting the semi-circular cage sections, in order to have access to the interior of the cage assembly for cleaning, replacement and/or repair of the screen bar members or other components, for example. In such arrangements, the installation and/or removal of the cage screen sections was not only difficult because of the weight of the component parts but was time consuming to accomplish resulting in considerable machine down-time. Accordingly, such prior screw press apparatus did not incorporate cage assemblies for dewatering purposes or the like which lent themselves to effective and efficient replacement of the component parts for cleaning, repair or the like.